Mg合金中の微視的異材界面における表面電位差が初期ガルバニック腐食現象へ及ぼす影響

概要

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Magnesium (Mg) is easy to be corroded in contact with other metals due to the formation of galvanic cell at the interface because it has the lowest negative standard electrode potential (SEP) in industrial metals. The traditional methods to evaluate corrosion resistance such as saltwater immersion test, salt spray test, and electrochemical corrosion test do not provide the effect of micro size metallic dispersoids on galvanic corrosion phenomena of Mg alloys, which is important and necessary. Therefore, in the present study, the corrosion resistance of Mg-Fe, Mg-Ni and Mg-Cu cast materials was evaluated using the surface potential difference (VSPD) at the interface between the dispersoids and α-Mg matrix of each material. Salt water immersion test of the cast materials was also conducted to clarify the relationship between this factor and corrosion rate of initial galvanic corrosion phenomena. Organizational structure of dispersoids and potential gradient between the dispersoids and the matrix had little effect on the corrosion rate of Mg alloy. Corrosion rate increased with increasing both VSPD at the interface and area fraction of the dispersoids in α-Mg matrix.